Apparatus and method for performing cell selection to home cell or private network in a mobile communication system

ABSTRACT

An apparatus and method for performing cell selection to a Home cell or a Private network in a mobile communication system are provided, in which a User Equipment (UE) determines a candidate cell by measuring a serving cell and neighbor cells, receives an indicator indicating a Home cell or a Private network in system information from the candidate cell, determines whether the candidate cell is included in a Home cell or Private network list set in the UE, and selects the candidate cell if the candidate cell is included in the Home cell or Private network list.

PRIORITY

This application is a Continuation of U.S. application Ser. No.12/015,182, now U.S. Pat. No. 8,036,656, which was filed in the U.S.Patent and Trademark Office on Jan. 16, 2008, and claims priority under35 U.S.C. §119(a) to a Korean Patent Application filed in the KoreanIntellectual Property Office on Jan. 16, 2007 and assigned Serial No.10-2007-0004900, the contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a mobile communicationsystem, and more particularly to an apparatus and method for performingcell selection to a Home cell or a Private network such that only aspecific User Equipment (UE) can access the Home cell or the Privatenetwork in a mobile communication system including public cells.

2. Description of the Related Art

Universal Mobile Telecommunications Systems (UMTS) is a 3^(rd)Generation (3G) asynchronous mobile communication system operating inWideband Code Division Multiple Access (WCDMA), based on European mobilecommunication systems, Global System for Mobile Communications (GSM) andGeneral Packet Radio Services (GPRS).

The 3^(rd) Generation Partnership Project (3GPP) that standardized UMTSis now discussing Long Term Evolution (LTE) as the next generation ofUMTS, Evolved UMTS.

The 3GPP LTE is a technology for enabling packet communications at orabove 100 Mbps, aiming at commercialization by the year 2010.

For deploying the LTE system, many communication schemes have beenproposed. Among them are schemes for reducing the number of nodes on acommunication line by simplifying a network configuration or foroptimizing radio protocols for radio channels.

FIG. 1 illustrates an Evolved UMTS mobile communication system to whichthe present invention is applied.

Referring to FIG. 1, an Evolved UMTS Radio Access Network (E-UTRAN) 110is simplified to a 2-node structure including Evolved Node Bs (ENBs)120, 122, 124 and an anchor node 130, or ENBs 126 and 128 and an anchornode 132.

A UE 101 is connected to an Internet Protocol (IP) network via theE-UTRAN 110. The ENBs 120 to 128 correspond to legacy Node Bs in theUMTS system and are connected to the UE 101 via radio channels. Comparedto the legacy Node Bs, the ENBs 120 to 128 handle more complex duties inthe system.

For example, since all user traffic including real-time service such asVoice Over IP (VoIP) is serviced on shared channels in the 3GPP LTE, anentity for collecting the status information of UEs and scheduling themis required and the ENBs 120 to 128 are responsible for the scheduling.Generally, an ENB controls a plurality of cells and performs AdaptiveModulation and Coding (AMC) by selecting a modulation scheme and achannel coding rate for a UE adaptively according to the channel statusof the UE.

As with High Speed Downlink Packet Access (HSDPA) and High Speed UplinkPacket Access (HSUPA) in UMTS, or Enhanced Dedicated CHannel (EDCH), theLTE system will use Hybrid Automatic Repeat reQuest (HARQ) between theENBs 120 to 128 and the UE 101.

Considering that a variety of Quality of Service (QoS) requirementscannot be fulfilled with HARQ, a high layer may perform an outer ARQbetween the UE 101 and the ENBs 120 to 128. HARQ is a technique forincreasing reception success rate by soft-combining previous receiveddata with retransmitted data without discarding the previous data.High-speed packet communication systems such as HSDPA or EDCH use HARQto increase transmission efficiency.

To realize a data rate of up to 100 Mbps, it is expected that the LTEsystem will adopt Orthogonal Frequency Division Multiplexing (OFDM) in a20-MHz bandwidth as a radio access technology.

To differentiate services from the legacy UMTS system, the 3GPP LTEstandard working group is considering using the Home cell or Privatenetwork for the LTE system. The Home cell or Private refers to a cell ora network that provides services only to a specific UE or UE Groups.

However, a cell (re)selection method for applying the Home cell or thePrivate network is yet to be specified and mentioned. Therefore,conventional methods of the legacy UMTS system for cell selectionassociated with movement of a UE are not viable in a mobilecommunication system where the Home cell or the Private network co-existwith macro cells (hereinafter public cells), because the conventionalcell selection methods do not involve the concept of the Home cell orthe Private network, as previously stated.

Another problem with the conventional cell selection in thecommunication system having the Home cell or the Private networktogether with the public cells is that all UEs consider the Home cell orthe Private network to be identical in a public cell and performs cellselection by a conventional measurement. Accordingly, there exists aneed for a more detailed cell selection method, considering theexistence of the Home cell or the Private network in the LTE system.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the problemsand/or disadvantages and to provide at least the advantages describedbelow. Accordingly, an aspect of the present invention is to provide amethod and apparatus for cell selecting to a specific cell as the Homecell or the Private network that only a specific UE or UE group canaccess the specific cell in a communication system that co-exists withpublic cells.

Another aspect of the present invention is to provide a method andapparatus of a UE for selecting to the Home cell or the Private networkby distinguishing the Home cell or the Private network from public cellsin a communication system that co-exists with public cells.

In accordance with the present invention, there is provided a method forperforming cell selection to a Home cell or a Private network in a UE ina mobile communication system, in which a candidate cell is determinedby measuring a serving cell and neighbor cells, an indicator indicatinga Home cell or a Private network is received in system information fromthe candidate cell, a determination is made as to whether the candidatecell is included in a Home cell or Private network list set in the UE,and the candidate cell is selected if it is included in the Home cell orPrivate network list.

In accordance with the present invention, there is provided a method forperforming cell selection to a Home cell or a Private network in a UE ina mobile communication system in which a neighbor cell list is received,the system including at least one neighbor cell with an offset in systeminformation from a serving cell, the offset indicating a Home cell or aPrivate network, the neighbor cell with the offset is extracted, adetermination is made as to whether the extracted neighbor cell isincluded in a Home cell or Private network list, the offset is added toa measurement of the extracted neighbor cell and the extracted neighborcell is selected as a candidate cell if the extracted neighbor cell isincluded in the Home cell or Private network list, system information isreceived from the candidate cell, and the candidate cell is selected.

In accordance with the present invention, there is provided an apparatusof a UE for performing cell selection to a Home cell or a Privatenetwork in a mobile communication system, in which a measurer determinesa candidate cell by measuring a serving cell and neighbor cells, anindicator analyzer receives an indicator indicating a Home cell or aPrivate network in system information from the candidate cell, anaccessibility decider determines whether the candidate cell is includedin a Home cell or Private network list set in the UE, and a cellre-selection decider selects the candidate cell if the candidate cell isincluded in the Home cell or Private network list.

In accordance with the present invention, there is provided an apparatusof a UE for performing cell selection to a Home cell or a Privatenetwork in a mobile communication system, in which a neighbor cell listreceives a neighbor cell list including at least one neighbor cell withan offset in system information from a serving cell, the offsetindicating a Home cell or a Private network, an extractor extracts theneighbor cell with the offset, an accessibility decider determineswhether the extracted neighbor cell is included in a Home cell orPrivate network list, and a cell re-selection decider adds the offset toa measurement of the extracted neighbor cell and selects the extractedneighbor cell as a candidate cell if the extracted neighbor cell isincluded in the Home cell or Private network list, receives systeminformation from the candidate cell, and selects the candidate cell.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates the configuration of a 3GPP LTE system to which thepresent invention is applied;

FIG. 2 illustrates a method for cell selecting to the Home cell or thePrivate network according to a first embodiment of the presentinvention;

FIG. 3 is a flowchart of an operation of a UE according to the firstembodiment of the present invention;

FIG. 4 is a flowchart of an operation of an ENB according to the firstembodiment of the present invention;

FIG. 5 is a block diagram of the UE according to the first embodiment ofthe present invention;

FIG. 6 is a block diagram of the ENB according to the first embodimentof the present invention;

FIG. 7 illustrates a method for cell selecting to the Home cell or thePrivate network according to the second embodiment of the presentinvention;

FIGS. 8A and 8B are flowcharts of an operation of the UE according tothe second embodiment of the present invention;

FIG. 9 is a flowchart of an operation of the ENB according to the secondembodiment of the present invention;

FIG. 10 is a block diagram of the UE according to the second embodimentof the present invention; and

FIG. 11 is a block diagram of the ENB according to the second embodimentof the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features and structures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The matters defined in the description such as a detailed constructionand elements are provided to assist in a comprehensive understanding ofpreferred embodiments of the invention. Accordingly, those of ordinaryskill in the art will recognize that various changes and modificationsof the embodiments described herein can be made without departing fromthe scope and spirit of the invention. Also, descriptions of well-knownfunctions and constructions are omitted for the sake of clarity andconciseness.

While preferred embodiments of the present invention are described inthe context of the 3GPP LTE system evolved from the 3GPP UMTS system, itis to be understood that the present invention is also applicable toother mobile communication systems where a UE performs cell(re)selection through UE measurement scheme.

The preferred embodiments of the present invention put forth a mobilecommunication environment and system that support a dedicated andspecialized service to a specific UE or a specific UE group byintroducing the Home cell or the Private network. The preferredembodiments of the present invention also provide a method forefficiently selecting and re-selecting the Home cell or the Privatenetwork according to a service provided to a UE in a mobilecommunication system where the Home cell or the Private network co-existwith public cells (macro cells).

Hereinbelow, the explanation of cell selection also applies to cellre-selection. The Home cell, Private network and office network cell aretypes of Closed Subscriber Group (CSG) cells, which are only accessibleby a specific UE or UE group. For the sake of convenience herein, theterms CSG cell, Home cell and Private network are interchangeably used.

Embodiment 1

A mobile communication system signals an indicator indicating whether atarget cell is a special cell accessible only to at least one specificUE, i.e. the Home cell or the Private network in broadcast systeminformation. If the indicator indicates the Home cell or the Privatenetwork, a UE compares cell information about the target cell with astored special list (hereinafter accessible list) including informationabout at least one specific Home cell or Private network accessible onlyto at least one specific UE. In the presence of the target cell in theaccessible list, the UE determines that the target cell is selectable orre-selectable. In the absence of the target cell in the accessible list,the UE determines that the target cell is not selectable orre-selectable.

For example, if a UE-selected Public Land Mobile Network (PLMN) isidentical to a PLMN for which information is broadcasted from the targetcell, the UE checks whether the accessible list includes a cellIDentifier (ID) received from the target cell. If the cell ID is uniqueirrespective of the PLMN, there is no need for comparing the PLMNs.

FIG. 2 illustrates a method for cell selecting to the Home cell or thePrivate network according to a first embodiment of the presentinvention.

Referring to FIG. 2, reference numeral 201 denotes a UE and referencenumeral 202 denotes a candidate (i.e. target) cell for cell selection,determined according to a measurement of the UE 201.

The UE 201 senses that a measurement has been triggered in step 211. Themeasurement is a process in which the UE 201 measures Primary-CommonPilot CHannels (P-CPICHs) received from a serving cell or neighbor cellsand determines the radio channel conditions of the serving cell or theneighbor cells.

The measurement is triggered when the UE 201 is powered-on, the UE 201needs to know the radio channel conditions of the neighbor cells forcell selection during movement, or the UE 201 needs to know the radiochannel conditions of the serving cell or the neighbor cellsperiodically.

In step 221, the UE 201 selects candidate cells for cell selectionaccording to the measurement result. In FIG. 2, one of the candidatecells is defined as a target cell 202.

When the target cell 202 is selected as a candidate cell for cellselection, the UE 201 receives system information broadcasted from thetarget cell 202 in step 231. The system information includes anindicator indicating whether the target cell 202 is the Home cell or thePrivate network that can service dedicated and specialized service tothe UE or the specific UE group including the UE. If the indicatorindicates that the target cell 202 is the Home cell or the Privatenetwork, the UE 201 performs steps 241, 243 and 245.

However, if the indicator does not indicate that the target cell 202 isthe Home cell or the Private network, the UE 201 performs step 251.

In step 241, the UE 201 searches for the target cell 202 in theaccessible list stored in the UE, wherein the accessible list includesspecific information about the Home cell or the Private network.

The UE 201 may store the accessible list in a memory such as a UniversalSubscriber Identity Module (USIM). The accessible list can be pre-storedby a hard coding scheme in the memory, or received from a network entityduring a Tracking Area Update (TAU) procedure.

That is, in step 241, the UE 201 checks whether the target cell 202 islisted in the accessible list including the Home cell or the Privatenetwork. If the target cell 202 is listed in the accessible list, i.e.the target cell 202 is an accessible cell such as the Home cell or thePrivate network, the UE 201 determines that the target cell 202 isselectable in step 243. Unless otherwise restricted, the UE 201 performscell selection to the target cell 202.

If the target cell 202 is not listed in the accessible list, the UE 201determines that the target cell 202 is not appropriate for cellselection in step 245. Thus, the UE 201 will select another candidatecell for cell selection.

The decision as to whether the target cell 202 is included in theaccessible list can be made from system information broadcasted from thetarget cell 202. That is, the UE 201 determines whether the cell ID ofthe target cell 202 in the system information is included in theaccessible list. If the cell ID is unique only in a PLMN, the UE 201should check whether a pair of the cell ID and the ID of the PLMN areincluded in the accessible list. It can be further contemplated that anID other than a cell ID is used, such as a Private network ID.

Meanwhile, in step 251, the UE 201 considers that the target cell 202 isa public cell and determines whether it is a selectable cell accordingto a conventional cell selection manner.

FIG. 3 is a flowchart of an operation of the UE according to the firstembodiment of the present invention.

Referring to FIG. 3, when the UE powers on or moves following the UEmobility, the UE selects a candidate cell for cell selection accordingto the measurement result and receives system information from thecandidate cell in step 301. The candidate cell can be set as a targetcell to which the UE prefers to move, by cell selection.

In step 303, the UE acquires an indicator indicating whether thecandidate cell is a special cell accessible only to the UE or a UEgroup, i.e. the Home cell or the Private network from the systeminformation. Since neither the UE nor UE group needs to share a radiolink with other unspecified UEs in a public cell, a QoS guarantee ismaximized for the UE or the UE group.

If the indicator indicates that the candidate cell is a Home cell or aPrivate network, the UE proceeds to step 311, where the UE compares acell ID of the candidate cell with the stored accessible list. Theaccessible list is stored by hard coding in a memory such as a USIM in3GPP system, or it is signaled from a higher network entity during aTracking Area Update (TAU) procedure and then stored in the memory inthe UE.

The comparison between the candidate cell with the accessible list is adetermination whether the candidate cell is included in the accessiblelist, and more particularly, whether the ID of candidate cell is matchedto a specific cell ID in the accessible list. If the candidate cell IDis unique only in a cell level, i.e., unique in a PLMN, the UE can checka pair of the candidate cell ID and the PLMN ID with the accessiblelist.

In the presence of the candidate cell ID in the accessible list, the UEdetermines that the candidate cell is the selectable (available) Homecell or Private network for the cell selection in step 321. Unlessrestricted by other information, the UE performs cell selection to thecandidate cell as the Home cell or Private network.

However, in the absence of the candidate cell ID of the candidate cellin the accessible list, the UE determines that the candidate cell is notavailable to access to the Home cell or Private network in step 323.

If the indicator does not indicate that the candidate cell is the Homecell or the Private network in step 305, the UE performs cell selectionin a conventional manner, considering the candidate cell to be a publiccell in step 331.

FIG. 4 is a flowchart of an operation of an ENB according to the firstembodiment of the present invention.

Referring to FIG. 4, the ENB sets system information to be broadcast toa specific cell managed by the ENB in step 401 and determines whetherthe cell is the Home cell or the Private network in step 403. The Homecell or the Private network can be set through Operations andMaintenance (O&M) or through signaling from a higher network entity.Thus, the ENB determines whether the cell is the set Home cell/Privatenetwork.

If the cell is the Home cell/Private network, the ENB sets an indicatorto indicate a special cell that only a predetermined UE or UE group canaccess in the system information in step 411.

However, if the cell is not a special cell, the ENB sets the indicatorto indicate a public cell (i.e., macro cell), and that it is not aspecial cell in the system information in step 413.

In step 421, the ENB broadcasts the set indicator in step 411 or step413 in a System Information Block (SIB) to the cell.

FIG. 5 is a block diagram of the UE according to the first embodiment ofthe present invention.

Referring to FIG. 5, a transceiver 501 receives a pilot signal for ameasurement from a candidate cell or receives system information from acandidate cell for cell selection according to the result of themeasurement.

A measurer 511 measures pilot signals received from the serving cell andneighbor cells of the UE through the transceiver 501 and determines thecandidate cell for cell selection according to the measurement.

After the candidate cell is selected in the measurer 511, an indicatoranalyzer 521 checks the system information of the candidate cellreceived from the transceiver 501 and analyzes an indicator in thesystem information.

A cell extractor 513 extracts ID information for identifying the cell orID information for estimating the mobility of the UE and stores theextracted ID information. For example, the ID information can be a cellID, a PLMN ID or a Private network ID.

The indicator analyzer 521 determines whether the indicator indicates aHome cell or a Private network.

An accessibility decider 523 determines whether the cell ID extracted bythe cell extractor 513 is included in a stored accessible list withinformation about accessible Home cells or Private networks stored in alist storage 525. The list storage 525 has already stored the accessiblelist in a USIM by hard coding, or has received the list from apredetermined higher network entity and stored it.

The result of the determination is provided as an input to a cellselection decider 531, for cell selection.

Meanwhile, if the indicator analyzer 521 determines that the candidatecell is not a Home cell or a Private network, the accessibility decider523 does not need to determine whether the candidate cell is accessiblethrough the cell extractor 513 and the list storage 525. Accordingly,the UE can determine in a conventional manner through the cell selectiondecider 531 whether the candidate cell is accessible. That is, the UEcan perform cell selection according to the measurements of neighborcells including the candidate cell, considering the candidate cell to bea public cell.

FIG. 6 is a block diagram of the ENB according to the first embodimentof the present invention.

Referring to FIG. 6, an indicator setter 601 sets an indicator for acell managed by the ENB by determining whether the cell is the Home cellor the Private network through Operations and Maintenance (O & M) orsignaling from a higher network entity.

Hence, when the cell is the Home cell or Private network, the indicatorsetter 601 sets the indicator to indicate a Home cell or a Privatenetwork in system information. If the cell is not a Home cell or aPrivate network, the indicator setter 601 sets the indicator to a publiccell in the system information. A transceiver 611 broadcasts the systeminformation including the indicator to all UEs within the cell.

Embodiment 2

A second embodiment of the present invention provides a method for, if aneighbor cell included in a neighbor cell list broadcast from a servingcell is a Home cell or a Private network, enabling only UEs that canaccess the neighbor cell to perform cell selection to the neighbor cellin a mobile communication system. An offset by which to prioritize theneighbor cell is optionally allocated so that if the offset is notincluded in information about the neighbor cell in the neighbor celllist, the UE performs a measurement in a conventional manner,considering that the neighbor cell is not a Home cell or a Privatenetwork.

If the offset is included in the neighbor cell information of theneighbor cell list, the UE compares a cell ID of the neighbor cell witha stored accessible list including information about accessible Homecells or Private networks. In the absence of the neighbor cell in theaccessible list, the UE deletes the neighbor cell from a measurementcontext, determining that the neighbor cell is not selectable. It can befurther contemplated that the UE performs the measurement, neglectingthe offset of the neighbor cell or applies the negative-signed value ofthe offset to the measurement of the neighbor cell, rather than onlyconsidering that the neighbor cell is not selectable.

However, if the neighbor cell is included in the accessible list, the UEapplies the positive-signed value of the offset to the measurement ofthe neighbor cell, considering that the neighbor cell is an accessibleHome cell or Private network, thus increasing the priority level of theneighbor cell for cell selection. The offset can be set to an infinitevalue.

The determination as to the presence or absence of the neighbor cell inthe accessible list can be made by checking whether a PLMN selected bythe UE is identical to a PLMN for which information is broadcast fromthe neighbor cell and the cell ID of the neighbor cell broadcast fromthe neighbor cell is included in the accessible list. If the cell ID isunique irrespective of the PLMN in the system, it may obviate the needfor checking whether the selected PLMN is the PLMN of the neighbor cell.

FIG. 7 illustrates a method for selecting a cell, considering a Homecell or a Private network according to the second embodiment of thepresent invention. This cell selection method is suitable for a cellre-selection scenario in the case of movement of a UE.

Referring to FIG. 7, reference numeral 701 denotes a UE and referencenumeral 702 denotes a serving cell for the UE 701.

In step 711, the serving cell 702 transmits a neighbor cell list to theUE 701 in system information. That is, the UE 701 receives the neighborcell list for use in a measurement in the system information broadcastfrom the serving cell 702. The neighbor cell list includes informationabout cells to be measured and cell selection parameters associated withthe cells, when the UE 701 needs to measure.

In the illustrated case of FIG. 7, the cell selection parameters includevalues from which information about the serving cell and a plurality ofneighbor cells can be estimated, such as frequency information or a cellID of each cell. That is, the neighbor cell list has cellselection-associated parameters, particularly the offset of a neighborcell being a Home cell or a Private network. For example, the offset canbe 3 db.

The offset functions to increase the priority level of the neighbor cellwhen a UE that can access the neighbor cell selects a candidate cell forcell selection as a result of the measurement. That is, when a pluralityof UEs that can access the neighbor cell measure their neighbor cells,they add the offset of the neighbor cell to the measurement of theneighbor cell.

For instance, the neighbor cell list includes parameters about neighborcell #1 to neighbor cell #8. If neighbor cell #6 is a Home cell or aPrivate network, the system information can be set as follows.

[Neighbor Cell List]

neighbor cell #1 information

neighbor cell #2 information

neighbor cell #3 information

neighbor cell #4 information

neighbor cell #5 information

neighbor cell #6 information: an offset for prioritizing neighbor cell#6

neighbor cell #7 information

neighbor cell #8 information

In step 721, the UE 701 extracts one or more neighbor cells withoffsets. In the above example, the UE 701 extracts neighbor cell #6.

The UE 701 determines whether the extracted neighbor cell (neighbor cell#6) exists in the accessible list including information about accessibleHome cells or Private networks in step 723.

The accessible list is stored by hard coding in a memory such as a 3GPPUSIM or signaled from a network entity during a TAU and stored. If thecell ID of the neighbor cell is unique only in a PLMN, the UE cancompare a pair of the cell and the ID of the PLMN with the list in step723.

The UE 701 deletes neighbor cells extracted in step 721 but not presentin the accessible list from a measurement context. That is, the UE 701considers these neighbor cells unselectable in steps 725 and 727, tothereby efficiently measure the remaining neighbor cells.

As the UE 701 moves and thus needs a measurement to ensure its mobility,it does not measure neighbor cells that satisfy the condition (i.e.having offsets) and that are not included in the accessible list byexcluding the neighbor cells from the measurement. As a result, themeasurement efficiency is increased. That is, the priority levels of theneighbor cells absent in the list in step 723 are decreased for cellselection because the neighbor cells are not accessible irrespective oftheir measurements. For example, if neighbor cell #6 is not included inthe accessible list, the UE 701 does not need to measure neighbor cell#6.

In step 731, the UE 701 senses that a measurement has been triggered forneighbor cells. For example, if the radio strength of the serving celldrops below a threshold, the measurement can be triggered.

The UE 701 measures neighbor cells listed in the neighbor cell list instep 741. Herein, the UE 701 measures neighbor cells with offsets amongthe neighbor cells of the neighbor cell list in order to prioritize Homecells or Private networks. At the same time, the UE 701 may not measureneighbor cells absent in the stored accessible list.

The neighbor cells measured in step 741 are those with offsets extractedin step 721. For a neighbor cell included in the stored list, the UE 701adds the offset of the neighbor cell to the measurement of the neighborcell in step 743.

This is done to increase the probability of an accessible Home cell orPrivate network being selected as a candidate cell for cell selection.That is, the UE gives a higher priority level to the cell for whichoffset is added to its measurement during cell selection. The offset ofeach Home cell or Private network may be different, and can be set to aninfinite value.

For a neighbor cell with an infinite offset, the UE 701 can select theneighbor cell immediately as a candidate cell for cell selection withoutmeasuring other neighbor cells and comparing their measurements.

In step 751, the UE 701 selects a candidate cell for cell selectionaccording to the measurements of the neighbor cells. The UE 701 receivescell selection-associated system information from the candidate cell,analyzes the cell selection-associated system information, and finallydetermines whether the candidate cell is to be selected in step 753.

FIGS. 8A and 8B are flowcharts of an operation of the UE according tothe second embodiment of the present invention.

Steps 801 to 833 of FIG. 8A concern an operation for receiving aneighbor cell list for a measurement in system information from aserving cell, and steps 841 to 857 of FIG. 8B concern a measurementoperation based on the neighbor cell list.

Referring to FIG. 8A, the UE receives a neighbor cell list for use in ameasurement from the serving cell in step 801.

In step 811, the UE extracts neighbor cells with offsets from theneighbor cell list. The offsets function to prioritize Home cells orPrivate networks, i.e. special cells accessible only to a predeterminedUE or UE group, during cell selection.

In step 813, the UE checks whether the extracted neighbor cells areincluded in the stored accessible list with information about accessibleHome cells or Private networks. The accessible list is stored by hardcoding in a memory such as a 3GPP USIM, or it is signaled from a networkentity during a TAU and then stored in the memory. If the cell IDs ofthe extracted neighbor cells are unique irrespective of PLMNs, the UEonly has to check whether the cell IDs are included in the accessiblelist. If the cell IDs are unique only in PLMNs, the UE can check whethercell ID-PLMN ID pairs are included in the accessible list.

If an extracted neighbor cell is not included in the accessible list,the UE deletes the neighbor cell from a measurement context, consideringthat the neighbor cell is not selectable in step 833. That is, theneighbor cell is not measured when the measurement is triggered, tothereby ensure the efficiency of the measurement operation.

However, if the neighbor cell exists in the accessible list, the UEstores ID information or the cell ID of the neighbor cell and its offsetin step 831.

FIG. 8B illustrates a measurement operation of the UE. In step 841, theUE senses that the measurement has been triggered for neighbor cells dueto the mobility of the UE, for example.

The UE measures the neighbor cells determined to be measured in step851. The UE may not measure neighbor cells that have offsets and thatare not included in the accessible list, for example, the neighbor cellsdeleted from the measurement context in step 833.

Meanwhile, the UE measures the neighbor cells that have offsets, arepresent in the accessible list, and thus are stored in step 831.

In step 853, the UE adds the offsets of the measured neighbor cells totheir measurements in order to prioritize Home cells or Private networksaccessible to the UE, for candidate cell selection. The UE can select aneighbor cell with the largest measurement as a candidate cell, unlessotherwise restricted. In step 855, the UE selects a candidate cell forcell selection from among the neighbor cells according to theirmeasurement results.

In step 857, the UE receives cell selection-associated systeminformation from the candidate cell and determines whether to select tothe candidate cell.

FIG. 9 is a flowchart of an operation of the ENB according to the secondembodiment of the present invention.

Referring to FIG. 9, the ENB sets a neighbor cell list for a cellmanaged by the ENB in step 901. The neighbor cell list can be broadcastin system information.

In step 903, the ENB determines whether a neighbor cell listed in theneighbor cell list is a Home cell or a Private network by O & M orthrough signaling from a higher network entity.

If the neighbor cell is a Home cell or a Private network in step 905,the ENB can explicitly or implicitly include an offset for the neighborcell in the neighbor cell list in step 911. The offset is used for a UEto prioritize the neighbor cell for cell selection.

If the neighbor cell is not a Home cell or a Private network, the ENBdoes not include an offset for the neighbor cell in the neighbor celllist in step 913.

When the offset setting is completed for every neighbor cell listed inthe neighbor cell list, the ENB broadcasts the neighbor cell list to thecell in the system information in step 921.

FIG. 10 is a block diagram of the UE according to the second embodimentof the present invention.

Referring to FIG. 10, a transceiver 1001 receives a pilot signal for ameasurement, receives a neighbor cell list in system information from aserving cell, or receives system information from a candidate cell forcell selection according to the result of the measurement.

A neighbor cell list receiver 1011 checks the neighbor cell list in thesystem information received from the transceiver 1001.

A neighbor cell extractor 1031 extracts neighbor cells with offsets fromthe neighbor cell list so that the UE that can access the neighbor cellsbeing Home cells or Private networks and prioritize them for cellselection using the offsets.

An accessibility decider 1033 determines whether the extracted neighborcells are accessible using a stored accessible list includinginformation about accessible Home cells or Private networks, stored in alist storage 1035. That is, the accessibility decider 1033 determineswhether the extracted neighbor cells are included in the accessiblelist.

If the cell ID of an extracted neighbor cell is not included in theaccessible list, a measurement context manager 1021 deletes the neighborcell from a measurement context.

Meanwhile, if the cell ID of the extracted neighbor cell is included inthe accessible list, a measurer 1041 measures the neighbor cell and addsits offset to its measurement in order to prioritize the neighbor cell,for selection of a Home cell or a Private network.

Therefore, a cell selection decider 1050 selects a candidate cell forcell selection according to the measurements received from the measurer1041, analyzes cell selection-associated system information receivedfrom the candidate cell, and selects the candidate cell being a Homecell or a Private network unless otherwise restricted.

FIG. 11 is a block diagram of the ENB according to the second embodimentof the present invention.

Referring to FIG. 11, a Home cell checker 1101 determines whether aneighbor cell listed in a neighbor cell list that a cell will transmitin system information is a special cell being a Home cell or a Privatenetwork accessible to a predetermined UE or UE group.

If the neighbor cell is a special cell, an offset setter 1103 sets anoffset for the neighbor cell to increase the probability of the neighborcell being selected for a UE that can access the neighbor cell.

If for every neighbor cell listed in the neighbor cell list, the Homecell checker 1101 completes the determination as to whether the neighborcell can operate as a Home cell or a Private network and the offsetsetter 1103 completes offset setting for neighbor cells being Home cellsor Private networks, a neighbor cell list setter 1105 completesformation of the neighbor cell list.

A transceiver 1111 broadcasts the neighbor cell list to all UEs withinthe cell in system information.

As is apparent from the above description, a UE compares cell IDinformation of a target cell received in system information with astored accessible list including information about Home cells or Privatenetworks and selects a Home cell or a Private network accessible to apredetermined UE or UE group as a candidate cell, for cell selection.Therefore, the UE receives a differentiated service that is dedicated tothe UE or UE group.

The UE compares the list with neighbor cells having offsets in aneighbor cell list received in system information from a serving celland selects a neighbor cell as a candidate cell for cell selection. Asthe measurements of the neighbor cells are prioritized using theoffsets, the reliability and efficiency of the measurement areincreased.

Further, since the UE deletes neighbor cells with a low probability ofoperating as Home cells or Private networks from a measurement context,the measurement process is simplified. That is, the UE deletes theneighbor cells from a measurement context and thus the measurementefficiency is maximized.

Also, higher priority levels are given to neighbor cells with a highprobability of operating as Home cells or Private networks. Hence, thereliability of cell selection after the measurement is ensured.

While the invention has been shown and described with reference tocertain exemplary embodiments of the present invention thereof, it willbe understood by those skilled in the art that various changes in formand details may be made therein without departing from the spirit andscope of the present invention as defined by the appended claims andtheir equivalents.

1. A method for performing cell selection to a Closed Subscriber Group(CSG) cell by a User Equipment (UE) in a mobile communication system,comprising: determining, by the UE, a candidate cell by measuringneighbor cells; receiving Public Land Mobile Network (PLMN) information,an indicator indicating information related to the CSG cell, and a CSGIDentification (ID) from the candidate cell; determining whether thecandidate cell belongs to a registered or selected PLMN, based on thePLMN information; determining whether the indicator indicates that theUE is accessible to the CSG cell; determining whether the CSG ID of thecandidate cell is included in a CSG list; and selecting the candidatecell, if the candidate cell belongs to the registered or selected PLMN,the indicator indicates that the UE is accessible to the CSG cell, andthe CSG ID of the candidate cell is included in the CSG list.
 2. Themethod of claim 1, further comprising storing the CSG list in aUniversal Subscriber Identity Module (USIM) of the UE.
 3. The method ofclaim 1, wherein the indicator indicates that the UE is accessible tothe CSG cell, if the CSG cell is included in the CSG list in the UE. 4.The method of claim 1, wherein the CSG list is signaled to the UE from ahigher network.
 5. The method of claim 1, wherein the CSG ID and theindicator indicating the information related to the CSG cell arereceived in system information from the candidate cell.
 6. The method ofclaim 1, further comprising identifying the candidate cell as anunselectable candidate, if the candidate cell is not included in the CSGlist.
 7. An apparatus of a User Equipment (UE) for performing cellselection to a Closed Subscriber Group (CSG) cell in a mobilecommunication system, comprising: a measurer for measuring neighborcells to determine a candidate cell; an indicator analyzer for receivingPublic Land Mobile Network (PLMN) information, an indicator indicatinginformation related to a CSG cell, and a CSG IDentification (ID) fromthe candidate cell; an accessibility decider for determining whether thecandidate cell belongs to a registered or selected PLMN, based on thePLMN information, determining whether the indicator indicates that theUE is accessible to the CSG cell, and determining whether the CSG ID ofthe candidate cell is included in a CSG list; and a cell re-selectiondecider for selecting the candidate cell, if the candidate cell belongsto the registered or selected PLMN, the indicator indicates that the UEis accessible to the CSG cell, and the CSG ID of the candidate cell isincluded in the CSG list.
 8. The apparatus of claim 7, wherein the CSGlist is stored in a Universal Subscriber Identity Module (USIM) of theUE.
 9. The apparatus of claim 7, wherein the indicator indicates thatthe UE is accessible to the CSG cell, if the CSG cell is included in theCSG list in the UE.
 10. The apparatus of claim 7, wherein the CSG listis signaled to the UE from a higher network.
 11. The apparatus of claim7, wherein the CSG ID and the indicator indicating information relatedto the CSG cell are received in system information from the candidatecell.
 12. The apparatus of claim 7, wherein the cell re-selectiondecider identifies the candidate cell as an unselectable candidate, ifthe candidate cell is not included in the CSG list.